Light Emitting Element, Electronic Device, and Method for Manufacturing Light Emitting Element

The present application is based on, and claims priority from JP Application Serial Number 2024-159104, filed Sep. 13, 2024, the disclosure of which is hereby incorporated by reference herein in its entirety.

The present disclosure relates to a light emitting element, an electronic device, and a method for manufacturing the light emitting element.

In the related art, as a light emitting element including a plurality of nanostructures, a light emitting element including a semiconductor substrate, a plurality of columnar nanostructures disposed on the semiconductor substrate, and an active layer disposed on the plurality of nanostructures has been known. The columnar nanostructure called nanocolumn, nanopillar, nanowire, or the like. The semiconductor material of the nanostructure of the light emitting element is selected according to a wavelength band of color light to be emitted. For example, a nitride-based compound is used for a nanostructure of a light emitting element that emits color light having a green wavelength band.

For example, JP-A-2008-244360 discloses a semiconductor light emitting element including an active layer made of a nitride-based compound semiconductor, an upper optical confinement layer and a lower optical confinement layer made of a nitride-based compound semiconductor having a superlattice structure and sandwiching the active layer, an upper cladding layer disposed above the upper optical confinement layer, and a lower cladding layer disposed below the lower optical confinement layer.

JP-A-2008-244360 is an example of the related art.

In the semiconductor light emitting element disclosed in JP-A-2008-244360, the optical confinement layers formed of a superlattice of indium gallium nitride (InGaN) and gallium nitride (GaN) are disposed above and below the active layer. In general, when a composition ratio of indium (In) in InGaN stacked on GaN is increased, a wavelength band of color light emitted from the semiconductor light emitting element becomes longer, and specifically, green light, red light, or light in an infrared wavelength band can be emitted. Meanwhile, when the composition ratio of In in InGaN is increased, a difference in lattice constant between InGaN and GaN increases, threading dislocations occur, the crystal quality degrades, and light emission characteristics of the semiconductor light emitting element deteriorate.

In the semiconductor light emitting element disclosed in JP-A-2008-244360, phase separation of the active layer is prevented by disposing the optical confinement layer above and below the active layer, the crystal quality is improved, and the light emission characteristics are improved. However, in a case of emitting color light having a relatively long wavelength band such as green light or red light among color light having a visible wavelength band from the semiconductor light emitting element disclosed in JP-A-2008-244360, when a thickness of the optical confinement layer is to be secured, it is difficult to avoid the occurrence of crystal defects, and there is a high possibility that the crystal quality of the optical confinement layer degrades and the light emission characteristics of the semiconductor light emitting element deteriorate. Therefore, there is a demand for measures for achieving both a sufficient thickness for optical confinement and restriction of occurrence of crystal defects.

A light emitting element according to an aspect of the present disclosure includes a first semiconductor layer having a first surface, a second semiconductor layer having conductivity different from that of the first semiconductor layer, a light emitting layer disposed between the first semiconductor layer and the second semiconductor layer, and a buffer layer disposed between the light emitting layer and the first semiconductor layer. The light emitting layer has a stacked body in which indium gallium nitride (InGaN) layers and gallium nitride (GaN) layers are alternately stacked, and has a second surface that is a facet plane. A composition ratio of In in the InGaN layer having a highest composition of In in the light emitting layer is 30% or more. The buffer layer has a third surface that is a facet plane. The composition ratio of In in the buffer layer is 20% or more.

Hereinafter, a light emitting element, an electronic device, and a method for manufacturing the light emitting element according to embodiments will be described with reference to the drawings. In the following drawings, dimensions and scales of parts are appropriately different from those of an actual device. Unless otherwise stated in the following description, the scope of the present disclosure is not limited to the embodiments described below.

10 10 10 12 19 13 14 10 1 FIG. 1 FIG. First, a projectoraccording to an embodiment of the present disclosure will be described.is a schematic diagram of the projector. As illustrated in, the projectoris a projection-type image display device that includes a light emitting device, a diffusion plate, a light modulation device, and a projection optical systemand projects an image on a screen SCR. The projectorcorresponds to an electronic device to be described later and an electronic device disclosed in the claims.

12 In the following description, an orthogonal coordinate system including an X axis, a Y axis, and a Z axis is used for describing each component. The Z axis is an axis parallel to an optical axis AX of light LC emitted from the light emitting devicedescribed below, and corresponds to, for example, a thickness direction or an up-down direction. One side of the Z axis is described as a −Z side, and the other side of the Z axis is described as a +Z side. The X axis and the Y axis are orthogonal to the Z axis and are orthogonal to each other. The X axis is, for example, parallel to a horizontal plane and corresponds to a left-right direction. One side of the X axis is described as a −X side, and the other side of the X axis is described as a +X side. The Y axis is, for example, parallel to a horizontal plane and corresponds to a depth direction. One side of the Y axis is described as a −Y side, and the other side of the Y axis is described as a +Y side.

12 12 20 21 The light emitting deviceemits the light LC, which is color light for projecting an image, to the +Z side along the optical axis AX parallel to the Z axis. The light emitting deviceincludes a light emitting elementand a heat sink.

20 20 20 20 20 20 20 22 20 20 20 20 a b a a b a b a The light emitting elementhas two end surfacesandand emits the light LC. The end surfaceof the two end surfaces is disposed on the +Z side, may have unevenness with respect to an XY plane including the X axis and the Y axis, may be a flat surface parallel to the XY plane, and has unevenness with respect to the XY plane, for example. When viewed along the Z axis, the end surfacesandof the light emitting elementand a light emitting region Ron the end surfacehave a rectangular shape. The end surfaceis a flat surface disposed on the −Z side of the end surfaceand parallel to the XY plane. A detailed configuration of the light emitting elementwill be described later.

20 20 10 10 a The light LC is emitted from the end surfaceof the light emitting elementtoward the +Z side along the optical axis AX. If the projectoris a device capable of displaying a full-color image, the light LC is, for example, white light including red light, green light, and blue light. If the projectoris a device capable of displaying a monochromatic image, the light LC is light of the same color as the monochromatic image, for example, any color light of red light, green light, and blue light.

21 20 20 20 b The heat sinkis disposed on the end surfaceof the light emitting elementand releases heat generated by the light emitting element.

19 12 19 19 The diffusion plateis disposed on an optical path of the light LC emitted from the light emitting device. The diffusion platediffuses the incident light LC on the XY plane and uniformizes illuminance of the light LC on the XY plane. The diffusion platemay be omitted.

13 12 19 13 The light modulation deviceis disposed on the optical path of the light LC emitted from the light emitting deviceand passing through the diffusion plate. The light modulation deviceis driven by receiving an electric signal input from an external input device or image forming device (not illustrated) via a control device (not illustrated), modulates the incident light LC according to image information included in the electric signal, and generates image light LM including a projection image.

13 16 17 18 The light modulation deviceincludes a light-incident-side polarizer, a liquid crystal element, and a light-exiting-side polarizer.

16 12 19 16 17 17 16 The light-incident-side polarizeris disposed on the optical path of the light LC emitted from the light emitting deviceand passing through the diffusion plate. For example, the light-incident-side polarizeris in contact with the liquid crystal elementfrom the −Z side, and may be disposed at an appropriate interval from the liquid crystal elementin the Z axis. The light-incident-side polarizerhas a polarization plane parallel to the XY plane, and emits predetermined polarized light of the incident light LC to the +Z side along the Z axis. The predetermined polarized light is, for example, P-polarized light.

17 16 26 17 26 17 22 20 26 17 22 20 The liquid crystal elementis disposed on the optical path of the predetermined polarized light LC emitted from the light-incident-side polarizer. A modulation plane including an image forming region Rof the liquid crystal elementis parallel to the XY plane. When viewed along the Z axis, the image forming region Rof the liquid crystal elementpresents a rectangular shape, and is substantially similar to the light emitting region Rof the light emitting elementin shape. Area of the image forming region Rof the liquid crystal elementis the same as or slightly smaller than area of the light emitting region Rof the light emitting element.

17 17 26 17 17 The liquid crystal elementis, for example, a transmissive liquid crystal panel. In the liquid crystal panel constituting the liquid crystal element, a plurality of pixels (not illustrated) are formed in a region corresponding to the image forming region Rof the liquid crystal element. The plurality of pixels are arranged along the X axis and the Y axis. The pixels each include a switching element. The switching element is, for example, a polysilicon thin film transistor (TFT). The liquid crystal elementemits the image light LM generated by the liquid crystal panel to the +Z side along the Z axis.

10 16 An electric signal corresponding to brightness of the color light at a relative position of each pixel in the image projected by the projectoris supplied from an external input device or image forming device to the switching element of the pixel of the liquid crystal panel. Each pixel of the liquid crystal panel modulates a vibration direction of the light LC, which is emitted from the light-incident-side polarizer, by the operation of the switching element according to the electric signal described above, and generates the image light LM having an illuminance distribution of color light according to the electric signal described above.

18 17 18 17 17 18 The light-exiting-side polarizeris disposed on the optical path of the image light LM emitted from the liquid crystal element. For example, the light-exiting-side polarizeris in contact with the liquid crystal elementfrom the +Z side, and may be disposed at an appropriate interval from the liquid crystal elementin the Z axis. The light-exiting-side polarizerhas a polarization plane parallel to the XY plane, and emits predetermined polarized light of the incident image light LM to the +Z side along the Z axis. The predetermined polarized light is, for example, P-polarized light.

16 18 10 12 16 10 17 18 The light-incident-side polarizerand the light-exiting-side polarizerare, for example, reflection type polarizing plates or absorption type polarizing plates. When it is desired to restrict generation of stray light inside the projectorand return light to the light emitting device, it is desirable to use an absorption type polarizing plate as the light-incident-side polarizer. When it is desired to restrict generation of stray light inside the projectoror return light to the liquid crystal element, it is desirable to use an absorption type polarizing plate as the light-exiting-side polarizer.

14 13 14 17 13 The projection optical systemis disposed on the optical path of the image light LM emitted from the light modulation device. The projection optical systemprojects the incident image light LM on the screen SCR disposed on the +Z side, and enlarges and displays an image, which is transmitted and output from the image forming device to the liquid crystal elementof the light modulation device, on the screen SCR.

20 20 20 2 FIG. Next, the light emitting elementaccording to an embodiment of the present disclosure will be described.is a plan view of the light emitting elementand corresponds to a view of the light emitting elementviewed from the +Z side along the Z axis.

2 FIG. 2 FIG. 20 20 22 24 22 57 22 57 57 a As illustrated in, the end surfaceof the light emitting elementis divided into the light emitting region Rincluding a center and a peripheral region Ron an outer peripheral side of the light emitting region Rwhen viewed along the Z axis. A plurality of nanocolumnsare formed in substantially the entire light emitting region Rat intervals along the X axis and the Y axis. Some of the plurality of nanocolumnsare illustrated in, and the remaining nanocolumnsare omitted.

2 FIG. 2 FIG. 57 57 57 57 As illustrated in, an interval Px between centers of two nanocolumnsadjacent to each other in the X axis and an interval Py between centers of two nanocolumnsadjacent to each other in the Y axis are, for example, 1 nm or more and 500 nm or less. For example, the intervals Px and Py are equal to each other, and the plurality of nanocolumnsare periodically arranged at intervals along each of the X axis and the Y axis. The plurality of nanocolumnsmay be arranged in, for example, a rectangular lattice shape, a triangular lattice shape, a honeycomb lattice shape, a cugome lattice shape, or a maple leaf lattice shape on a surface parallel to the XY plane, in addition to being arranged in a square lattice shape when viewed from the +Z side along the Z axis as illustrated in.

57 57 57 57 57 57 22 22 A distance Dx between the nanocolumnsandlocated at both ends of the plurality of nanocolumnsarranged along the X axis and a distance Dy between the nanocolumnsandlocated at both ends of the plurality of nanocolumnsarranged along the Y axis are appropriately set according to a size of the light emitting region Ralong the X axis and a size of the light emitting region Ralong the Y axis.

3 FIG. 2 FIG. 3 FIG. 20 20 50 55 56 57 52 53 is a cross-sectional view of the light emitting elementtaken along a line III-III in. As illustrated in, the light emitting elementincludes a substrate, a semiconductor layer, a mask layer, a plurality of the nanocolumns, and conductive layersand.

50 20 50 50 50 a b The substrateconstitutes a base of the light emitting elementand has a front surfaceand a back surfaceparallel to the XY plane. The substrateis, for example, a silicon (Si) substrate, a GaN substrate, or a sapphire substrate.

50 50 55 50 50 55 50 67 57 20 a a In the embodiment, a sapphire substrate having a C-plane of plane orientation is used as the substrate. Since the substrateis the sapphire substrate, when the semiconductor material of the semiconductor layerformed at the front surfaceon the +Z side of the substrateis GaN, crystal quality of the semiconductor layermade of GaN is high, and uniform crystal is formed at the front surface. As a result, a current uniformly flows through a semiconductor layerof the nanocolumn, and light emission efficiency of the light emitting elementis improved.

55 50 50 55 a The semiconductor layeris formed at the front surfaceon the +Z side of the substrate. The semiconductor layeris formed of, for example, an n-type GaN layer doped with Si.

55 50 50 55 55 22 57 55 24 50 55 50 55 a a b A bottom surface of the semiconductor layeron the −Z side is in contact with the front surfaceof the substrate. In the semiconductor layer, as will be described later, a semiconductor layerA of the light emitting region Rin which the plurality of nanocolumnsare formed in the XY plane on the +Z side protrudes further to the +Z side than a semiconductor layerB of the peripheral region R. The front surfaceof the semiconductor layerA is located on the +Z side of the back surfaceof the semiconductor layerB.

56 55 56 56 56 56 57 57 56 57 55 55 a The mask layeris formed at a front surface of the semiconductor layerA on the +Z side. The mask layeris formed of, for example, a layer containing titanium (Ti). A dimension of the mask layerin the Z axis, that is, a thickness of the mask layeris, for example, about 5 nm. A plurality of through holes are formed in the mask layerin accordance with positions where the plurality of nanocolumnsare formed. The plurality of through holes act as openings, and the nanocolumnsgrow from the through holes to the +Z side as described later. The mask layeris a mask layer for forming the nanocolumnsin a plurality of selective small regions exposed to the +Z side by the plurality of through holes in a front surfaceof the semiconductor layerA.

57 55 55 56 57 55 67 57 a The plurality of nanocolumnsare formed in the plurality of small regions of the front surfaceof the semiconductor layerA that are exposed without being covered with the mask layer. Each nanocolumnis a columnar crystal structure extending from the semiconductor layerA to the +Z side along the Z axis, and is a nanostructure. Light emitted from the semiconductor layeras a light emitting layer is emitted not only to the +Z side along the Z axis but also to a direction parallel to the XY plane and the −Z side. Therefore, a mirror may be provided on a side surface side or a back surface side of the nanocolumn, and a reflection structure for increasing the light emitted to the +Z side may be provided.

57 57 57 57 57 57 57 57 57 57 A shape of the nanocolumnwhen viewed along the Z axis, that is, a shape of the nanocolumnin plan view is, for example, a polygon or a circle. When the semiconductor material of the nanocolumncontains GaN, the shape of the nanocolumnin plan view is a hexagon. A maximum width of the nanocolumnwhen viewed along the Z axis, that is, a diameter of the nanocolumnis on the order of nm, and is, for example, 100 nm or more and 300 nm or less. When the shape of the nanocolumnin plan view is a polygon, the diameter of the nanocolumnmeans the diameter of the smallest circle containing the polygon therein. When the shape of the nanocolumnin plan view is an ellipse, the diameter of the nanocolumnmeans the diameter of the smallest circle containing the ellipse therein.

57 57 57 57 57 57 When the shape of the nanocolumnin plan view is a circle, the center of the nanocolumnmeans the center of the circle. When the shape of the nanocolumnin plan view is a polygon, the center of the nanocolumnmeans the center of the smallest circle containing the polygon therein. When the shape of the nanocolumnin plan view is an ellipse, the center of the nanocolumnmeans the center of the smallest circle containing the ellipse therein.

57 65 66 67 68 65 66 67 68 66 67 68 The nanocolumnincludes semiconductor layers,,, and. The semiconductor layers,,, andare sequentially stacked from the −Z side to the +Z side along the Z axis. The semiconductor layers,, andare formed by epitaxial growth as described later.

65 57 55 56 55 55 22 55 65 65 55 a The semiconductor layeris disposed on the most −Z side of the nanocolumn, is formed in the small region of the semiconductor layerthat is not covered with the mask layeron the front surfaceof the semiconductor layerA in the light emitting region R, and extends from the semiconductor layerA to the +Z side along the Z axis. The semiconductor layercorresponds to a first semiconductor layer described later and a first semiconductor layer disclosed in the claims. The semiconductor layeris made of the same semiconductor material as the semiconductor layer, and is formed of, for example, an n-type GaN layer doped with Si.

65 65 65 65 65 65 65 a a a A front surfaceof the semiconductor layeron the +Z side is inclined with respect to the XY plane, and extends to the +Z side as approaching a center thereof from an outer periphery thereof as viewed along the Z axis. The front surfaceof the semiconductor layeron the +Z side is formed by epitaxially growing n-type GaN in the formation of the semiconductor layer, and is narrowed on the +Z side toward the center as viewed along the Z axis. The front surfaceof the semiconductor layercorresponds to a first surface described later and a first surface disclosed in the claims.

66 65 65 66 The semiconductor layeris disposed on the semiconductor layeron the +Z side and is stacked on the semiconductor layeron the +Z side. The semiconductor layercorresponds to a buffer layer described later and a buffer layer disclosed in the claims.

66 65 65 65 65 a a A bottom surface of the semiconductor layeron the −Z side is in contact with the front surfaceof the semiconductor layerfrom the +Z side, is inclined at the same angle as the front surfaceof the semiconductor layerwith respect to the XY plane, and extends to the +Z side as approaching a center thereof from an outer periphery thereof as viewed along the Z axis.

66 66 66 66 66 66 66 66 a a A front surfaceof the semiconductor layeron the +Z side is inclined at an angle larger than the bottom surface of the semiconductor layeron the −Z side with respect to the XY plane, and extends to the +Z side as approaching a center thereof from an outer periphery thereof as viewed along the Z axis. A distance in the z axis between an outer peripheral end and the center of the front surfaceof the semiconductor layeris larger than a distance in the Z axis between an outer peripheral end and the center of the bottom surface of the semiconductor layeron the −Z side. A dimension of the semiconductor layerin the Z axis, that is, a thickness of the semiconductor layerincreases from the outer periphery toward the center.

66 The semiconductor layeris implemented by a layer formed of a superlattice (SL) of InGaN and GaN. The layer formed of the superlattice of InGaN and GaN is formed of a stacked body in which an InGaN layer and a GaN layer are alternately stacked along the Z axis. A Z-axis dimension of the InGaN layer in the superlattice of InGaN and GaN, that is, a thickness of the InGaN layer is, for example, about 5 nm. A Z-axis dimension of the GaN layer in the superlattice of InGaN and GaN, that is, a thickness of the GaN layer is about the same as the thickness of the InGaN layer, and is, for example, about 5 nm.

66 66 a The front surfaceof the semiconductor layeron the +Z side corresponds to a third surface described later and a third surface disclosed in the claims, is a facet plane, and is, for example, a (10-11) surface of the layer formed of the superlattice of InGaN and GaN.

66 66 66 66 66 20 66 A dimension of the outer peripheral end of the semiconductor layerin the Z axis, that is, a thickness of the outer peripheral end of the semiconductor layeris, for example, 100 nm or more and 400 nm or less. An average composition ratio of In in the semiconductor layeris adjusted according to the thickness of the semiconductor layer. The semiconductor layeracts as pseudo mixed crystal of InGaN in which the average composition ratio of In is adjusted according to the thickness. In the light emitting elementof the embodiment, the average composition ratio of In in the semiconductor layeris at least higher than 18%, preferably 20% or more, and more preferably 25% or more and less than 30%.

66 66 66 66 65 65 a a When the average composition ratio of In in the semiconductor layeris about 22%, the angle formed by the front surfaceof the semiconductor layerwith respect to the XY plane is about 60°, and the angle formed by the front surface of the semiconductor layeron the −Z side and the front surfaceof the semiconductor layerwith respect to the XY plane is about 30°.

67 66 66 67 The semiconductor layeris disposed at the semiconductor layeron the +Z side and is stacked on the semiconductor layeron the +Z side. The semiconductor layercorresponds to an active layer, and corresponds to a light emitting layer described later and a light emitting layer disclosed in the claims.

67 66 66 66 66 67 67 66 66 67 67 67 a a a a A bottom surface of the semiconductor layeron the −Z side is in contact with the front surfaceof the semiconductor layerfrom the +Z side, is inclined at the same angle as the front surfaceof the semiconductor layerwith respect to the XY plane, and extends to the +Z side as approaching a center thereof from an outer periphery thereof as viewed along the Z axis. A front surfaceof the semiconductor layeron the +Z side is inclined at the same angle as the front surfaceof the semiconductor layerand the bottom surface of the semiconductor layeron the −Z side with respect to the XY plane, and extends to the +Z side as approaching a center thereof from an outer periphery thereof as viewed along the Z axis. A dimension of the semiconductor layerin the Z axis, that is, a thickness of the semiconductor layeris substantially uniform in the XY plane from the outer periphery to the center.

67 67 a The front surfaceof the semiconductor layercorresponds to a second surface described later and a second surface disclosed in the claims, is a facet plane, and is, for example, a (10-11) surface of a layer having a multi-quantum well (MQW) structure of InGaN and GaN.

67 The semiconductor layerhas a stacked structure of an InGaN layer and a GaN layer, and has an MQW. The stacked structure of the InGaN layer and the GaN layer is a stacked body in which the InGaN layer and the GaN layer are alternately stacked along the Z axis.

67 67 66 67 67 20 67 66 67 The dimension of the semiconductor layerin the Z axis, that is, the thickness of the semiconductor layeris, for example, 20 nm or more and 200 nm or less. Similarly to the semiconductor layer, an average composition ratio of In in the semiconductor layeris adjusted according to the thickness of the semiconductor layer. In the light emitting elementof the embodiment, the composition ratio of In in the InGaN layer having the highest In composition in the semiconductor layeris at least higher than the average composition ratio of In in the semiconductor layerand is 30% or more, for example, 33% or more and 35% or less. The average composition ratio of In in the semiconductor layeris desirably 30% or more.

66 67 67 67 a For example, when the average composition ratio of In in the semiconductor layeris about 22% and the average composition ratio of In in the semiconductor layeris about 33%, the angle formed by the front surfaceof the semiconductor layerwith respect to the XY plane is about 60°.

66 67 20 66 67 67 67 66 65 67 65 67 A band gap of InGaN contained in the semiconductor layersandis relatively narrow compared to that in other semiconductor materials. In the light emitting elementof the embodiment, the semiconductor layerin which the average composition ratio of In is lower than that of the semiconductor layeris disposed as a buffer layer on the −Z side of the semiconductor layeras an active layer, that is, below the semiconductor layer. By disposing the semiconductor layerbetween the semiconductor layerand the semiconductor layer, a difference in lattice constant between the semiconductor layercontaining n-type GaN and the semiconductor layercontaining InGaN is relaxed.

66 66 66 57 57 a Since the average composition ratio of In in the semiconductor layeris higher than that in a semiconductor layer of a light emitting element in the related art, the semiconductor layerhaving the front surfaceand formed of a superlattice of InGaN and GaN is disposed at a portion on the +Z side of a center of the nanocolumnin a direction along the Z axis, that is, at an upper portion of the nanocolumn, as a hexagonal pyramidal structure having a (10-11) facet plane.

66 20 66 66 66 66 66 67 66 66 67 20 a a a Although the average composition ratio of In in the semiconductor layerin the light emitting elementof the embodiment is at least lower than 18%, it has been confirmed that the (10-11) surface appears well on the front surfaceeven when the average composition ratio of In in the semiconductor layeris about 16% as described later. When the average composition ratio of In in the semiconductor layeris excessively low, for example, less than 15%, a (10-12) surface, a (10-13) surface, or the like may coexist in addition to the (10-11) surface on the front surfaceof the semiconductor layer. In this case, the crystal quality and characteristics of the semiconductor layergrowing from the front surfaceof the semiconductor layerto the +Z side become non-uniform in a plane parallel to the XY plane, threading dislocations and defects occur in the semiconductor layer, and the light emission efficiency of the light emitting elementmay decrease.

66 67 67 66 66 66 20 67 20 a When the average composition ratio of In in the semiconductor layeris 20% or more, In smoothly enters the semiconductor layerwhen the semiconductor layerhaving a higher average composition ratio of In is grown from the front surfaceof the semiconductor layer. By disposing the semiconductor layer, even when a temperature of an environment in which the light emitting elementis manufactured is relatively high, the desired semiconductor layerin which the average composition ratio of In is high and is 30% or more is obtained, and the light emission efficiency of the light emitting elementis improved.

20 20 67 When a current is injected into the light emitting element, carriers are satisfactorily recombined, and luminance of the light LC emitted from the light emitting elementis improved. In the semiconductor layer, since the composition ratio of In in the InGaN layer having the highest In composition is 30% or more, and for example, the average composition ratio of In is 30% or more and relatively high, the wavelength band of the light LC can be easily a longer red wavelength band among visible wavelength bands.

68 67 67 68 68 55 The semiconductor layeris disposed on the semiconductor layeron the +Z side and is stacked on the semiconductor layeron the +Z side. The semiconductor layercorresponds to a second semiconductor layer described later and a second semiconductor layer disclosed in the claims. The semiconductor layeris made of a semiconductor material having conductivity different from that of the semiconductor layer, and is formed of, for example, a p-type GaN layer doped with magnesium (Mg).

68 67 67 a A bottom surface of the semiconductor layeron the −Z side is inclined at the same angle as the front surfaceof the semiconductor layerwith respect to the XY plane, and extends to the +Z side as approaching a center thereof from an outer periphery thereof as viewed along the Z axis.

56 68 57 68 67 57 2 2 3 An insulating layer (not illustrated) may be formed at a front surface of the mask layeron the +Z side. A front surface of the insulating layer (not illustrated) on the +side is at the same position as a front surface of the semiconductor layerof the plurality of nanocolumnson the +Z side in the Z axis, and constitutes substantially the same surface as the front surface of the semiconductor layeron the +Z side. A refractive index of the insulating layer (not illustrated) is lower than an effective refractive index of the semiconductor layerof the nanocolumn. The insulating layer (not illustrated) is formed of, for example, a silicon oxide (SiO) layer or an aluminum oxide (AlO) layer.

52 57 55 55 24 55 52 67 57 55 65 66 57 52 20 67 57 a The conductive layeris disposed on a side of the plurality of nanocolumnsin the XY plane, and is formed at the front surfaceof the semiconductor layerB in the peripheral region Rof the semiconductor layer. The conductive layeris electrically coupled to the semiconductor layerof the nanocolumnvia the semiconductor layerand the semiconductor layerandof the nanocolumn. The conductive layercorresponds to a first electrode of the light emitting element, and is one electrode for injecting a current into the semiconductor layerof the nanocolumn.

52 The conductive layeris formed of a layer made of a conductive material, and may be formed of, for example, an aluminum (Al) layer or a gold (Au) layer, or may be formed of a layer formed of a stacked body in which a Ti layer, an Al layer, and an Au layer are stacked in this order on the +Z side.

53 57 68 53 67 68 57 53 20 67 57 The conductive layeris disposed on the +Z side, that is, on an upper side of the plurality of nanocolumns, and is formed over front surfaces of the plurality of semiconductor layerson the +Z side. The conductive layeris electrically coupled to the semiconductor layervia the semiconductor layerof the nanocolumn. The conductive layercorresponds to a second electrode of the light emitting element, and is the other electrode for injecting a current into the semiconductor layerof the nanocolumn.

53 The conductive layeris formed of a layer made of a conductive material, for example, Indium Tin Oxide (ITO), and may be formed of an Al layer or an Au layer.

20 68 57 67 65 65 68 67 52 53 67 In the light emitting element, the p-type semiconductor layerof the nanocolumn, the semiconductor layernot doped with impurities, and the n-type semiconductor layerconstitute a pin diode. A band gap in the semiconductor layersandis larger than the band gap in the semiconductor layer. When a forward bias voltage corresponding to the pin diode is applied between the conductive layersandand a current is injected, recombination of electrons and holes occurs in the semiconductor layer, and light is generated.

20 20 4 6 FIGS.to 2 FIG. Next, a method for manufacturing the light emitting elementaccording to an embodiment of the present disclosure will be described.are cross-sectional views illustrating the method for manufacturing the light emitting element, and correspond to views taken along a line III-III in.

55 50 50 155 50 50 55 50 50 a a a First, a process of forming the semiconductor layeron the front surfaceof the substrateis performed by stacking a substratemade of n-type GaN crystal or the like on the +Z side of the front surfaceof the substratesuch as a sapphire substrate. Alternatively, the semiconductor layermay be formed by epitaxially growing an n-type GaN layer on the front surfaceof the substrateby a metal organic chemical vapor deposition method or the like.

4 FIG. 5 FIG. 56 55 55 56 57 55 55 56 55 55 56 56 57 56 55 57 55 55 a a a a a Subsequently, as illustrated in, the mask layerformed of a Ti layer or the like having a thickness of about 5 nm is formed at the front surfaceof the semiconductor layer. Thereafter, as illustrated in, a process of patterning the mask layerin accordance with the arrangement of the plurality of nanocolumnson the XY plane to form a small region, in which the front surfaceof the semiconductor layeris exposed, is performed. For example, a deposition method or the like may be used to form the mask layeron the entire surfaceof the semiconductor layer. For patterning the mask layer, electron beam (EB) lithography, dry etching, or the like may be used. By patterning the mask layer, a plurality of openings corresponding to relative arrangement of the plurality of nanocolumnsare formed in the mask layer, and the front surfaceof the small region in which the plurality of nanocolumnsare formed in the front surfaceof the semiconductor layeris exposed.

5 FIG. 57 55 56 57 65 66 67 68 56 65 66 67 68 56 Next, as illustrated in, a process of forming the nanocolumnin the small region of the semiconductor layernot covered with the mask layerfrom the +Z side is performed. In order to form the nanocolumn, a molecular beam epitaxy (MBE) method, a metal organic chemical vapor deposition (MOCVD) method, or the like may be used. By using appropriate growth conditions for each of the semiconductor layers,,, and, the mask layeracts as a selective growth mask, and each of the columnar semiconductor layers,,, andgrows in the opening of the mask layerand extends to the +Z side along the Z axis.

57 65 66 67 68 65 66 67 68 In the process of growing the nanocolumnto the +Z side along the Z axis, in a growth stage of each of the columnar semiconductor layers,,, and, the amount of irradiation of the semiconductor material of each semiconductor layer is appropriately adjusted from the +Z side and an outer peripheral side in the XY plane with respect to the formation region of the columnar body, that is, from obliquely above. The appropriate growth conditions for each of the semiconductor layers,,, andinclude an irradiation rate of the semiconductor material of each semiconductor layer.

57 53 68 57 22 56 24 55 24 52 55 55 a Although not illustrated, after a plurality of nanocolumnsare formed, the conductive layeris formed over the semiconductor layerof the plurality of nanocolumnsin the light emitting region Rcorresponding to a display region by using electrode patterning or the like. The mask layerin the peripheral region Ris removed, a +Z side portion of the semiconductor layerin the peripheral region Ris removed using dry etching or the like, and the conductive layeris formed at the front surfaceof the semiconductor layerB by using electrode patterning or the like.

20 3 FIG. The light emitting elementillustrated incan be manufactured by performing the above-described processes.

20 20 Next, a protype example of the light emitting elementof the present embodiment will be described. The element of the prototype example was manufactured based on the configuration and the manufacturing method of the light emitting elementdescribed above.

7 FIG. 8 FIG. 7 FIG. 7 8 FIGS.and 57 20 66 67 66 67 57 is a high-angle annular dark field scanning transmission electron microscopy (HAADF-STEM) image of a plurality of nanocolumnsof the light emitting elementaccording to the first prototype example.is an enlarged view of a part of the HAADF-STEM image of. In the first prototype example, an average composition ratio of In in the semiconductor layerwas assumed to be 25%, and an average composition ratio of In in the semiconductor layerwas assumed to be 33%. From, it can be confirmed that the high-quality semiconductor layersandin which crystal defects are hardly observed are formed in the columnar nanocolumns.

8 FIG. 67 67 67 67 As illustrated in, a semiconductor layerA that can act as a barrier layer formed of a superlattice of InGaN and GaN was formed in a portion of the semiconductor layeron the −Z side. A semiconductor layerB acting as an MQW of InGaN and GaN was formed in a portion of the semiconductor layeron the +Z side.

9 FIG. 8 FIG. 9 FIG. 66 67 is a graph showing average composition ratios of In and Ga in a range of a line IX-IX in. As illustrated in, the average composition ratio of In in the semiconductor layerwas about 25% as assumed, and the average composition ratio of In in the semiconductor layerwas about 33% as assumed.

10 FIG. 10 FIG. 65 66 57 20 66 66 57 is an HAADF-STEM image of the semiconductor layersandof a plurality of nanocolumnsof the light emitting elementaccording to a second prototype example. In the second prototype example, an average composition ratio of In in the semiconductor layerwas assumed to be 16%. From, it can be confirmed that the high-quality semiconductor layerin which crystal defects are hardly observed is formed in the columnar nanocolumns.

11 FIG. 10 FIG. 11 FIG. 66 is a graph showing average composition ratios of In and Ga in a range of a line XI-XI in. As illustrated in, the average composition ratio of In in the semiconductor layerwas about 16% as assumed.

20 65 68 67 66 65 65 68 65 65 68 67 65 68 66 65 68 20 67 67 67 66 66 66 a a a The light emitting elementof the embodiment described above includes the semiconductor layer (first semiconductor layer), the semiconductor layer (second semiconductor layer), the semiconductor layer (light emitting layer), and the semiconductor layer (buffer layer). The semiconductor layerhas the front surface (first surface)on the +Z side. The semiconductor layerhas conductivity different from that of the semiconductor layer. In the embodiment, the semiconductor layerhas n-type conductivity, whereas the semiconductor layerhas p-type conductivity. The semiconductor layeris disposed between the semiconductor layersandin the Z axis. The semiconductor layeris disposed between the semiconductor layersandin the Z axis. In the light emitting elementof the embodiment, the semiconductor layerhas a stacked body in which InGaN layers and GaN layers are alternately stacked in the Z axis, and has the front surface (second surface)that is a facet plane. A composition ratio of In in the InGaN layer having the highest composition of In in the semiconductor layeris 30% or more. The semiconductor layerhas the front surface (third surface)that is a facet plane. The composition ratio of In in the semiconductor layeris at least 18% or more, and preferably 20% or more.

20 57 57 66 65 67 67 66 67 20 65 67 66 67 67 67 66 67 57 67 In the light emitting elementof the embodiment, in the light emitting element including the nanocolumn, the nanocolumnincludes the semiconductor layercontaining InGaN and GaN as a buffer layer between the semiconductor layercontaining n-type GaN and the semiconductor layercontaining InGaN and GaN as a light emitting layer. The InGaN layer having the highest composition of In in the semiconductor layerhas a high composition ratio of In of 30% or more, whereas an average composition ratio (composition ratio) of In in the semiconductor layeris lower than the composition ratio of In in the InGaN layer having the highest ratio of In in the semiconductor layerand is 20% or more and less than 30%. In the light emitting elementof the embodiment, since a difference in lattice constant between the semiconductor layersandis relaxed by the semiconductor layer, the occurrence of crystal defects in the semiconductor layercan be restricted, the high-quality semiconductor layercan be formed, and the light LC in the red wavelength band on the long wavelength side in the visible wavelength band can be emitted from the semiconductor layer. That is, it is possible to achieve both sufficient thicknesses of the semiconductor layersandfor light confinement in the nanocolumnsand restriction of occurrence of crystal defects in the semiconductor layer.

20 65 65 a In the light emitting elementof the embodiment, the front surfaceof the semiconductor layeris a facet plane.

20 65 65 66 66 65 20 20 a a a According to the light emitting elementof the embodiment, since a (10-11) surface as a facet plane is formed at the front surfaceof the semiconductor layer, the (10-11) surface can be provided using the front surfaceas a facet plane without excessively increasing the thickness of the semiconductor layergrown on the +Z side of the front surface. This can simplify the manufacturing process of the light emitting elementof the embodiment and reduce a size of the light emitting element.

20 66 In the light emitting elementof the embodiment, the semiconductor layeris a superlattice layer that is a stacked body in which InGaN layers and GaN layers are alternately stacked in the Z axis.

20 66 65 67 20 According to the light emitting elementof the embodiment, since the semiconductor layeris formed of a superlattice of InGaN and GaN, the difference in lattice constant between the semiconductor layersandis more smoothly relaxed, and illuminance distribution and the amount of light LC emitted from the light emitting elementcan be stabilized.

10 12 20 The projectoraccording to the embodiment includes the light emitting deviceincluding the light emitting elementaccording to the embodiment.

10 20 20 According to the projectorof the embodiment, since the high-quality light emitting elementis provided, characteristics of the image light LM based on the light LC emitted from the light emitting elementcan be improved, and display quality of a projection image can be improved.

20 Examples of an electronic device including the light emitting elementaccording to the embodiment include a head mounted display (HMD) and a printer in addition to the projector.

20 65 66 67 68 50 50 55 50 66 66 67 67 a a a a A method for manufacturing a light emitting element according to the embodiment is a method for manufacturing the light emitting element, and includes a process of sequentially forming the semiconductor layers,,, andon the front surfaceof the substratevia the semiconductor layeralong a direction parallel to the Z axis intersecting the front surface. In the above process, the (10-11) surface (third surface), which is a facet plane, is developed on the front surfaceof the semiconductor layeron the +Z side, and the (10-11) surface (second surface), which is a facet plane, is developed on the front surfaceof the semiconductor layeron the +Z side.

20 According to the method for manufacturing the light emitting element of the embodiment, the high-quality light emitting elementcan be manufactured.

Preferable embodiments the of present disclosure have been described above in detail. The present disclosure is, however, not limited to the specific embodiments, and various modifications and changes can be made within the scope of the gist of the present disclosure disclosed in the claims.

A summary of the present disclosure is appended below.

a first semiconductor layer having a first surface; a second semiconductor layer having conductivity different from that of the first semiconductor layer; a light emitting layer disposed between the first semiconductor layer and the second semiconductor layer; and a buffer layer disposed between the light emitting layer and the first semiconductor layer, in which the light emitting layer has a stacked body in which indium gallium nitride (InGaN) layers and gallium nitride (GaN) layers are alternately stacked, and has a second surface that is a facet plane, a composition ratio of indium (In) in each of the InGaN layers having a highest composition of In in the light emitting layer is 30% or more, the buffer layer has a third surface that is a facet plane, and the composition ratio of In in the buffer layer is 20% or more. (Appendix 1) A light emitting element including:

In the configuration of Appendix 1, since a difference in lattice constant between the first semiconductor layer and the light emitting layer is relaxed by the buffer layer and the occurrence of crystal defects in the light emitting layer is restricted, a high-quality light emitting layer can be formed. With the configuration of Appendix 1, it is possible to achieve both sufficient thicknesses of the buffer layer and the light emitting layer for light confinement in a nanocolumn of the light emitting element and restriction of occurrence of crystal defects in the light emitting layer.

the first surface is a facet plane. (Appendix 2) The light emitting element according to Appendix 1, in which

According to the configuration of Appendix 2, the third surface can be provided as a facet plane without excessively increasing the thickness of the buffer layer grown on the first surface.

the buffer layer is a superlattice layer that is a stacked body in which InGaN layers and GaN layers are alternately stacked. (Appendix 3) The light emitting element according to Appendix 1 or 2, in which

According to the configuration of Appendix 3, a difference in lattice constant between the first semiconductor layer and the light emitting layer is more smoothly relaxed, and illuminance distribution and the amount of light emitted from the light emitting element can be stabilized.

the light emitting element according to any one of Appendices 1 to 3. (Appendix 4) An electronic device including:

According to the configuration of Appendix 4, it is possible to improve characteristics of image light based on light emitted from the light emitting element and to improve the display quality of an image displayed by the image light.

a process of sequentially forming the first semiconductor layer, the buffer layer, the light emitting layer, and the second semiconductor layer on a front surface of a substrate along a direction intersecting the front surface, in which in the process, a second surface that is a facet plane of the light emitting layer is developed, and a third surface that is a facet plane of the buffer layer is developed. (Appendix 5) A method for manufacturing the light emitting element according to any one of Appendices 1 to 3, the method including:

With the configuration of Appendix 5, a high-quality light emitting element can be provided as described above.